Abstract

The complement system plays an important role in the protection of the organism from infection. A key step in complement activation is the proteolytic cleavage of C3 protein resulting in a soluble anaphylatoxin C3a peptide and C3b protein that is able to form a covalent bond with surface molecules of microbial cells. The activity of C3b is regulated by its subsequent limited proteolysis with the release of the C3f peptide, which is believed to have no functional activity itself. Based on the physicochemical properties of C3f, we hypothesized that this peptide may exhibit antimicrobial activity. Complement activation usually takes place on the surface of pathogens, in particular, bacterial cells, and local generation of antimicrobial peptides can contribute significantly to their neutralization. The antimicrobial activity of complement derivatives, C3a and C4a peptides, is already known from the literature. To study the antimicrobial properties of C3f, we obtained this peptide by the method of solid-phase synthesis. It has been shown that human C3f exhibits moderate antimicrobial activity in vitro against certain gram-positive bacteria (Listeria monocytogenes, Micrococcus luteus, Enterococcus faecium) with minimal inhibitory concentrations of 70 μM (for L. monocytogenes) or higher. The revealed antimicrobial activity of C3f is much lower than the activity of C3a described in the literature. Several microorganisms (Bacillus cereus, Escherichia coli, Candida albicans) were resistant to C3f.

中文翻译：

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评估 C3f 肽（人 C3 蛋白衍生物）的抗菌活性

摘要

补体系统在保护生物体免受感染方面起着重要作用。补体激活的关键步骤是 C3 蛋白的蛋白水解裂解，产生可溶性过敏毒素 C3a 肽和 C3b 蛋白，它们能够与微生物细胞的表面分子形成共价键。C3b 的活性受其随后有限的蛋白水解和 C3f 肽释放的调节，据信其本身没有功能活性。基于 C3f 的理化特性，我们假设该肽可能具有抗菌活性。补体激活通常发生在病原体，特别是细菌细胞的表面，局部产生的抗菌肽可以显着促进它们的中和。补体衍生物的抗菌活性，C3a 和 C4a 肽已从文献中获知。为了研究 C3f 的抗菌特性，我们通过固相合成的方法获得了这种肽。已经表明，人类 C3f 在体外对某些革兰氏阳性菌表现出中等的抗菌活性。单核细胞增生李斯特菌、藤黄微球菌、屎肠球菌）的最小抑制浓度为 70 μM（对于单核细胞增生李斯特菌）或更高。所揭示的 C3f 的抗菌活性远低于文献中描述的 C3a 的活性。几种微生物（蜡状芽孢杆菌、大肠杆菌、白色念珠菌）对 C3f 具有抗性。